In-medium screening effects for the Galactic halo and solar-reflected dark matter detection in semiconductor targets

TL;DR

This paper develops a practical DFT-based method to estimate dark matter-electron scattering rates in semiconductors, highlighting the significance of in-medium screening effects for both galactic and solar-reflected dark matter detection.

Contribution

It introduces a DFT approach for calculating DM-electron scattering rates in semiconductors and compares the effects of local field effects on detection sensitivity.

Findings

In-medium screening significantly affects detection rates in semiconductor targets.

The DFT method shows consistency and robustness in estimating excitation event rates.

Screening effects vary with the energy regime of reflected dark matter particles.

Abstract

Recently, the importance of the electronic many-body effect in the dark matter (DM) detection has been recognized and a coherent formulation of the DM-electron scattering in terms of the dielectric response of the target material has been well established in literatures. In this paper, we put relevant formulas into practical density functional theory (DFT) estimation of the excitation event rates for the diamond and silicon semiconductor targets. Moreover, we compare the event rates calculated from the energy loss functions with and without the local field effects. For a consistency check of this numerical method, we also compare the differential spectrum and detection reach of the silicon with those computed with the $\mathtt{GPAW}$ code. It turns out that this DFT approach is quite consistent and robust. As an interesting extension, we also investigate the in-medium effect on the detection of the solar-reflected DM flux in silicon-based detectors, where the screening effect is found to be also remarkable in the optically thick regime, and to turn insignificant in the optically thin regime, depending on the energies of the reflected DM particles.